CN105742702B

CN105742702B - Rechargeable lithium battery

Info

Publication number: CN105742702B
Application number: CN201510983176.8A
Authority: CN
Inventors: 高濑浩成; 横辻北斗
Original assignee: Samsung SDI Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 2014-12-26
Filing date: 2015-12-24
Publication date: 2020-03-31
Anticipated expiration: 2035-12-24
Also published as: US20160190644A1; EP3038194A1; CN105742702A; US10541444B2; EP3038194B1

Abstract

A rechargeable lithium battery includes: a positive electrode including a positive active material; and an electrolyte solution including a solvent and an additive, wherein the positive active material includes a lithium-containing transition metal oxide, the solvent includes a hydrofluoroether, and the additive includes: the first additive represented by chemical formula 1 is selected from at least one of the second additive represented by chemical formula 2, the third additive represented by chemical formula 3, and the fourth additive represented by chemical formula 4.

Description

Rechargeable lithium battery

Technical Field

One or more aspects of embodiments of the present disclosure relate to a rechargeable lithium battery.

Background

A rechargeable lithium battery may include a positive active material layer electrochemically inserting and extracting lithium ions and an electrolyte solution in which the lithium ions are dissolved. The electrolyte solution may be impregnated in the porous separator.

For example, rechargeable lithium batteries utilizing a separator having pores (which have two different characteristics) and including a fluorinated ether in an electrolyte solution have been described as having improved cycle life.

However, there is a strong competition in cost in the area of batteries suitable for use in portable electronic devices (e.g., mobile devices) such as smart phones, tablets, and the like. For example, the use of solid solution oxides as positive electrode materials can be expensive, and thus conventional transition metal oxides including lithium such as lithium cobalt oxide are commonly used to achieve high voltage batteries.

For application in batteries with such positive electrode materials, electrolyte solutions comprising hydrofluoroethers have recently been proposed. However, when such an electrolyte solution is used for a rechargeable lithium battery using a transition metal oxide including lithium as a positive electrode material, the cycle life and storage characteristics of the battery may be deteriorated when stored at high temperatures.

Disclosure of Invention

One or more aspects of embodiments of the present disclosure provide a rechargeable lithium battery having improved cycle-life characteristics and storage characteristics at high temperatures.

One embodiment provides a rechargeable lithium battery including: a positive electrode including a positive active material; and an electrolyte solution including a solvent and an additive, wherein the positive active material includes a lithium-containing transition metal oxide, and the solvent includes a first additive represented by chemical formula 1 and at least one selected from a second additive represented by chemical formula 2, a third additive represented by chemical formula 3, and a fourth additive represented by chemical formula 3.

Chemical formula 1

In chemical formula 1, R¹To R³May each be independently selected from the group consisting of a C1 to C8 alkyl group substituted or unsubstituted with a vinyl group or a C1 to C5 alkyl group and not including a double bond, a C1 to C8 alkyl group substituted or unsubstituted with a vinyl group or a C1 to C5 alkyl group and including a double bond, a C1 to C8 alkyl group, a C2 to C8 alkenyl group, a C5 to C8 cycloalkyl group, a C6 to C8 aryl group and a fluorine atom,

R⁴may be selected from C1 to C8 alkylene groups, C2 to C8 alkynylene groups, C4 to C8 alkylene groups having at least one selected from ether groups and thioether groups, a compound having a plurality of-CF groups₂-C1 to C8 alkylene groups of linking groups and C4 to C10 alkylene groups with ether and thioether groups.

Chemical formula 2

In the chemical formula 2, the first and second organic solvents,

R⁵may be selected from C2 to C6 alkylene groups having no double bond, C2 to C6 alkylene groups having a double bond, and C6 to C12 alkenyl groups,

R⁶to R¹¹May each be independently selected from C1 to C6 alkyl groups and C2 to C6 alkenyl groups.

Chemical formula 3

In the chemical formula 3, the first and second,

R¹²and R¹³May each be independently selected from hydrogen and C1 to C8 alkyl,

R¹⁴may be selected from C1 to C8 alkyl, C2 to C8 alkenyl, C2 to C8 alkynyl and C1 to C8 haloalkyl groups substituted or unsubstituted with vinyl groups.

Chemical formula 4

In the chemical formula 4, the first and second organic solvents,

R¹⁵and R¹⁶May each be independently selected from hydrogen and C1 to C8 alkyl,

R¹⁷may be selected from C1 to C8 alkyl, C2 to C8 alkenyl, C2 to C8 alkynyl and C1 to C8 haloalkyl,

n may be 1 or 2.

The Hydrofluoroether (HFE) may comprise 2,2, 2-trifluoroethyl methyl ether (CF)₃CH₂OCH₃) 2,2, 2-trifluoroethyl difluoromethyl ether (CF)₃CH₂OCHF₂) 2,2,3,3, 3-Pentafluoropropylmethyl ether (CF)₃CF₂CH₂OCH₃) 2,2,3,3, 3-Pentafluoropropyldifluoromethyl ether (CF)₃CF₂CH₂OCHF₂) 2,2,3,3, 3-pentafluoropropyl-1, 1,2, 2-tetrafluoroethyl ether (CF)₃CF₂CH₂OCF₂CF₂H) 1,1,2, 2-tetrafluoroethylmethyl ether (HCF)₂CF₂OCH₃) 1,1,2, 2-tetrafluoroethylethyl ether (HCF)₂CF₂OCH₂CH₃) 1,1,2, 2-tetrafluoroethylpropyl ether (HCF)₂CF₂OC₃H₇) 1,1,2, 2-tetrafluoroethylbutyl ether (HCF)₂CF₂OC₄H₉) 2,2,3, 3-tetrafluoroethyl difluoromethyl ethane (H (CF)₂)₂CH₂O(CF₂) H), 1,2, 2-tetrafluoroethyl isobutyl ether (HCF)₂CF₂OCH₂CH(CH₃)₂) 1,1,2, 2-tetrafluoroethyl isoamyl ether (HCF)₂CF₂OCH₂C(CH₃)₃) 1,1,2, 2-tetrafluoroethyl-2, 2, 2-trifluoroethyl ether (HCF)₂CF₂OCH₂CF₃) 1,1,2, 2-tetrafluoroethyl-2, 2,3, 3-tetrafluoropropyl ether (HCF)₂CF₂OCH₂CF₂CF₂H) Hexafluoroisopropyl methyl ether ((CF)₃)₂CHOCH₃) 1,1,3,3, 3-pentafluoro-2-trifluoromethylpropyl methyl ether ((CF)₃)₂CHCF₂OCH₃) 1,1,2,3,3, 3-hexafluoropropyl methyl ether (CF)₃CHFCF₂OCH₃) 1,1,2,3,3, 3-hexafluoropropylethyl ether (CF)₃CHFCF₂OCH₂CH₃) 2,2,3,4,4, 4-hexafluorobutyldifluoromethyl ether (CF)₃CHFCF₂CH₂OCHF₂) Or mixtures thereof.

The hydrofluoroether may be included in an amount of about 10 vol% to about 60 vol%, based on the total volume of the solvent.

The first additive may be included in an amount of about 0.01 wt% to 1.5 wt%, based on the total weight of the electrolyte solution.

When the additives include the first additive and the second additive, the second additive may be included in an amount of about 0.05 wt% to about 1.00 wt%, based on the total weight of the electrolyte solution.

When the additives include the first additive and the third additive, the third additive may be included in an amount of about 0.04 wt% to about 1.00 wt%, based on the total weight of the electrolyte solution.

When the additives include the first additive and the fourth additive, the fourth additive may be included in an amount of about 0.01 wt% to about 1.00 wt%, based on the total weight of the electrolyte solution.

The first additive may include at least one selected from the group consisting of compounds represented by chemical formulas 1-1 to 1-9.

Chemical formula 1-1

Chemical formula 1-2

Chemical formulas 1 to 3

Chemical formulas 1 to 4

Chemical formulas 1 to 5

Chemical formulas 1 to 6

Chemical formulas 1 to 7

Chemical formulas 1 to 8

Chemical formulas 1 to 9

The second additive may include a compound represented by chemical formula 2-1, a compound represented by chemical formula 2-2, or a mixture thereof.

Chemical formula 2-1

Chemical formula 2-2

The third additive may include at least one selected from the group consisting of compounds represented by chemical formulas 3-1 to 3-8.

Chemical formula 3-1

Chemical formula 3-2

Chemical formula 3-3

Chemical formula 3-4

Chemical formula 3-5

Chemical formula 3-6

Chemical formula 3-7

Chemical formula 3-8

The fourth additive may include at least one selected from the compounds represented by chemical formulas 4-1 to 4-4.

Chemical formula 4-1

Chemical formula 4-2

Chemical formula 4-3

Chemical formula 4-4

The lithium-containing transition metal oxide may be a lithium cobalt-based composite oxide.

The rechargeable lithium battery may further include a negative electrode including a negative active material, wherein the negative active material includes at least one selected from the group consisting of a carbon-based material, a silicon-based material, a tin-based material, a lithium metal oxide, and metallic lithium.

The solvent may also include fluoroethylene carbonate.

Fluoroethylene carbonate may be included in an amount of about 10 to 30 vol%, based on the total volume of the solvent.

The redox potential of the rechargeable lithium battery may be greater than or equal to about 4.3V (vs. Li/Li)⁺) And less than or equal to about 5.0V.

Other embodiments of the present disclosure are included in the following detailed description.

A rechargeable lithium battery having improved cycle-life characteristics and storage characteristics at high temperatures can be realized.

Drawings

Fig. 1 is a sectional view illustrating a rechargeable lithium battery according to one or more embodiments of the present disclosure.

Fig. 2 is a graph showing charge transfer efficiency in LiCoO after the rechargeable lithium battery cells according to example 1 and comparative example 1 are stored at 60 ℃ for 24 hours₂Scanning Electron Microscope (SEM) photograph of the state of the passivation film on the surface of the particles.

Detailed Description

Hereinafter, embodiments of the present disclosure are described in more detail. However, these example embodiments are provided for illustrative purposes, and the present disclosure is not limited thereto.

As used herein, unless the context indicates otherwise, it will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present.

Hereinafter, a rechargeable lithium battery according to one or more embodiments of the present disclosure is described with reference to fig. 1.

Referring to fig. 1, a rechargeable lithium battery 10 includes a positive electrode 20, a negative electrode 30, and a separator layer 40.

The rechargeable lithium battery 10 can have, for example, greater than or equal to about 4.3V (vs. Li/Li)⁺) And is smaller thanOr equal to about 5.0V to a voltage (e.g., oxidation-reduction potential), and in some embodiments, greater than or equal to about 4.4V and less than or equal to about 5.0V.

The shape of the rechargeable lithium ion battery 10 is not particularly limited, and the battery may have any suitable shape such as a shape of a cylinder, a prismatic laminate type (e.g., a prismatic laminate), a button, or the like.

The positive electrode 20 includes a current collector 21 and a negative electrode active material layer 22.

Current collector 21 may be any suitable conductor (e.g., any suitable material having electrically conductive properties), and may include, for example, aluminum, stainless steel, and/or nickel plated steel.

The positive electrode active material layer 22 includes a positive electrode active material, and may further include a conductive material and a binder.

The positive active material according to one embodiment may include a lithium-containing transition metal oxide.

The lithium-containing transition metal oxide can be, for example, LiCoO₂Lithium cobalt-based composite oxide such as LiNi_xCo_yMn_zO₂Lithium nickel cobalt manganese-based composite oxide such as LiNiO₂Or a lithium nickel-based composite oxide such as LiMn₂O₄The lithium manganese-based composite oxide of (1). The positive electrode active material may include one of the foregoing materials, or a mixture of two or more thereof. According to the embodiments of the present disclosure, when a combination of electrolyte solution additives (described in more detail later) is used as an electrolyte solution, it is possible to prevent or reduce deterioration of cycle-life characteristics and storage characteristics of a battery at high temperatures due to the use of a lithium cobalt-based composite oxide.

The content of the positive electrode active material (for example, the amount of the positive electrode active material included in the positive electrode active material layer of the rechargeable lithium battery) is not particularly limited, and any suitable amount of the positive electrode active material may be included.

The conductive material may be, for example: carbon black such as ketjen black, acetylene black, and the like; natural graphite; artificial graphite, etc., but the conductive material is not so limited and may include any suitable material capable of improving the conductivity of the positive electrode.

The content of the conductive material (e.g., the amount of the conductive material included in the positive active material layer of the rechargeable lithium battery) is not particularly limited, and the conductive material may be included in any suitable amount.

The binder may be, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber (SBR), nitrile rubber, fluoroelastomer, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, or the like, but the binder is not so limited, and may include any suitable binder as long as it can bind the positive electrode active material and the conductive material on the current collector and can exhibit oxidation resistance and electrolyte solution stability sufficient to withstand the high potential of the positive electrode.

The content of the binder (e.g., the amount of the binder included in the positive active material layer of the rechargeable lithium battery) is not particularly limited, and any suitable amount of the binder may be included.

The density of the positive electrode active material layer 22 is not particularly limited. The density of the cathode active material layer 22 can be calculated by dividing the surface density of the cathode active material layer 22 after compression by the density of the cathode active material layer 22 after compression.

The positive electrode active material layer 22 can be manufactured by using, for example, the following method. The positive electrode material mixture is manufactured, for example, by dry-blending the positive electrode active material, the conductive agent, and the binder. Subsequently, the positive electrode material mixture is dispersed in an appropriate or suitable organic solvent (such as N-methyl-2-pyrrolidone, for example) to form a positive electrode material mixture slurry, the positive electrode material mixture slurry is coated on the current collector 21, dried and pressed to form a positive electrode active material layer.

The negative electrode 30 includes a current collector 31 and a negative electrode active material layer 32.

The current collector 31 may be any conductor (e.g., any suitable material having electrically conductive properties) and may include, for example, copper (Cu), copper alloys, aluminum, stainless steel, nickel plated steel, and the like.

The negative active material layer 32 may be any negative active material layer suitable for use in a rechargeable lithium battery. For example, the anode active material layer 32 may include an anode active material, and may further include a binder.

The anode active material may include a carbon-based material, a silicon-based material, a tin-based material, a lithium metal oxide, and the like, which may be used singly (e.g., singly) or in a mixture of two or more. The carbon-based material may be, for example, a graphite-based material such as artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, or the like. The silicon-based material may be, for example, silicon oxide, silicon-containing alloys, mixtures of any of the foregoing materials and graphite-based materials, and the like. The silicon oxide may be formed from SiO_x(wherein, 0<x is less than or equal to 2). The tin-based material may be, for example, tin oxide, tin-containing alloys, mixtures of any of the foregoing materials and graphite-based materials, and the like. The lithium metal oxide may be, for example, a titanium oxide-based compound (such as Li)₄Ti₅O₁₂)。

For example, the anode active material may be a mixture of a carbon-based material such as a graphite-based material and a silicon-based material such as a silicon-containing alloy. The carbon-based material and the silicon-based material may be mixed in a weight ratio of about 50:50 to about 90:10 (e.g., about 60:40 to about 80: 20). The silicon content of the silicon-containing alloy (e.g., the amount of silicon included in the silicon-containing alloy) may be greater than or equal to about 50 wt% based on the total amount of the silicon-containing alloy. According to one embodiment, when the anode active material includes a silicon-based material, the cycle-life characteristics and storage characteristics of the battery at high temperature may be significantly improved as compared to the case of the battery without the silicon-based material.

The description of the binder may be the same as that of the binder of the positive electrode active material layer 22.

The content of the binder (e.g., the amount of the binder included in the negative active material layer of the rechargeable lithium battery) is not particularly limited, and any suitable amount of the binder may be included.

The anode active material layer 32 may further include a thickener such as carboxymethyl cellulose (CMC). The weight ratio of thickener to binder may be greater than or equal to about 1/10 and less than or equal to about 10/10.

The density of the anode active material layer 32 is not particularly limited. The density of the anode active material layer 22 can be calculated by dividing the surface density of the anode active material layer 32 after compression by the thickness of the anode active material layer 32 after compression.

The negative electrode 30 may be manufactured by using a method such as the following. First, a negative electrode active material and a binder are dispersed in a solvent such as water and N-methylpyrrolidone to prepare a slurry, and then the slurry is coated on the current collector 31 and dried.

Separator layer 40 includes a separator and an electrolyte solution.

The separator is not particularly limited and may be any separator suitable for use in a rechargeable lithium battery.

The separator may include a porous layer, a non-woven fabric having excellent high-rate discharge properties, or a mixture thereof.

The separator may be made of a material including, for example, polyolefin-based resin, polyester-based resin, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-ethylene-tetrafluoroethylene copolymer, or the like. The polyolefin-based resin may be, for example, polyethylene, polypropylene, etc., and the polyester-based resin may be, for example, polyethylene terephthalate, polybutylene terephthalate, etc.

The thickness of the separator is not particularly limited.

The electrolyte solution may include a lithium salt, a solvent, and an additive.

The lithium salt may be used as an electrolyte of the electrolyte solution. The lithium salt may be, for example, LiPF₆、LiClO₄、 LiBF₄、LiAsF₆、LiSbF₆、LiSO₃CF₃、LiN(SO₂CF₃)、LiN(SO₂CF₂CF₃)、 LiC(SO₂CF₂CF₃)₃、LiC(SO₂CF₃)₃、LiI、LiCl、LiF、LiPF₅(SO₂CF₃)、LiPF₄(SO₂CF₃)₂And the like. One or more lithium salts may be dissolved in the electrolyte solution.

In some embodiments, the lithium salt dissolved in the electrolyte solution improves the battery characteristics.

The concentration of the lithium salt is not particularly limited, but may be about 0.85mol/L to about 1.6mol/L, for example, about 0.9mol/L to about 1.40 mol/L. When the concentration of the lithium salt is within any of these ranges, the battery characteristics may be improved.

According to one embodiment of the present disclosure, the solvent may include Hydrofluoroether (HFE).

Here, Hydrofluoroethers (HFEs) may refer to ethers in which one or more hydrogens have been replaced with fluorine, and HFEs may be used to improve oxidation resistance.

The Hydrofluoroether (HFE) may be selected from 2,2, 2-trifluoroethyl methyl ether (CF) depending on the resistance and charging voltage (e.g., charging voltage) of the current density used for the positive electrode material₃CH₂OCH₃) 2,2, 2-trifluoroethyl difluoromethyl ether (CF)₃CH₂OCHF₂) 2,2,3,3, 3-Pentafluoropropylmethyl ether (CF)₃CF₂CH₂OCH₃) 2,2,3,3, 3-Pentafluoropropyldifluoromethyl ether (CF)₃CF₂CH₂OCHF₂) 2,2,3,3, 3-pentafluoropropyl-1, 1,2, 2-tetrafluoroethyl ether (CF)₃CF₂CH₂OCF₂CF₂H) 1,1,2, 2-tetrafluoroethylmethyl ether (HCF)₂CF₂OCH₃) 1,1,2, 2-tetrafluoroethylethyl ether (HCF)₂CF₂OCH₂CH₃) 1,1,2, 2-tetrafluoroethylpropyl ether (HCF)₂CF₂OC₃H₇) 1,1,2, 2-tetrafluoroethylbutyl ether (HCF)₂CF₂OC₄H₉) 2,2,3, 3-tetrafluoroethyl difluoromethyl ether (H (CF)₂)₂CH₂O(CF₂) H), 1,2, 2-tetrafluoroethyl isobutyl ether (HCF)₂CF₂OCH₂CH(CH₃)₂) 1,1,2, 2-tetrafluoroethyl isoamyl ether (HCF)₂CF₂OCH₂C(CH₃)₃) 1,1,2, 2-tetrafluoroethyl-2, 2, 2-trifluoroethyl ether (HCF)₂CF₂OCH₂CF₃) 1,1,2, 2-tetrafluoroethyl-2, 2,3, 3-tetrafluoropropyl ether (HCF)₂CF₂OCH₂CF₂CF₂H) Hexafluoroisopropyl methyl ether ((CF)₃)₂CHOCH₃) 1,1,3,3, 3-pentafluoro-2-trifluoromethylpropyl methyl ether ((CF)₃)₂CHCF₂OCH₃) 1,1,2,3,3, 3-hexafluoropropyl methyl ether (CF)₃CHFCF₂OCH₃) 1,1,2,3,3, 3-hexafluoropropylethyl ether (CF)₃CHFCF₂OCH₂CH₃) 2,2,3,4,4, 4-hexafluorobutyldifluoromethyl ether (CF)₃CHFCF₂CH₂OCHF₂) And mixtures thereof. For example, the HFE may be selected in view of the charging voltage of the battery and the resistance of the positive electrode material (at a given or set current density of the battery). Any of the foregoing materials may be used singly (e.g., singly) or in mixtures of two or more.

The content (e.g., amount) of the hydrofluoroether is not particularly limited, and may be about 10% by volume to about 60% by volume, for example, about 30% by volume to about 50% by volume or about 35% by volume to about 50% by volume, based on the total volume of the solvent. When the content of the hydrofluoroether is within any of these ranges, the battery characteristics can be improved.

The solvent may include a non-aqueous solvent, which may be any non-aqueous solvent suitable for use in a rechargeable lithium battery, in addition to the hydrofluoroether, without particular limitation.

The non-aqueous solvent may be selected from, for example: cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, vinylene carbonate, and the like; linear carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like; cyclic esters such as γ -butyrolactone, γ -valerolactone, and the like; linear esters such as methyl formate, methyl acetate, methyl butyrate, and the like; tetrahydrofuran and derivatives thereof; ethers such as 1, 3-dioxane, 1, 4-dioxane, 1, 2-dimethoxyethane, 1, 4-dibutoxyethane, methyldiglyme and the like; nitriles such as acetonitrile, benzonitrile, and the like; dioxolane and derivatives thereof; and episulfide, sulfolane, sultone and derivatives thereof, which may be used singly (e.g., singly) or in a mixture of two or more, without limitation. When two or more nonaqueous solvents are used, the mixing ratio of the two or more solvents is not particularly limited and may be any ratio suitable for use in a rechargeable lithium battery. In some embodiments, one or more linear carbonates may be used as the non-aqueous solvent.

The linear carbonate may be present in an amount (e.g., amount) of about 5 vol% to about 60 vol%, for example, about 20 vol% to about 50 vol%, based on the total volume of the solvent. When the content of the linear carbonate is within any of these ranges, the battery performance may be improved.

The solvent may also include fluoroethylene carbonate.

The fluoroethylene carbonate can be present in an amount (e.g., amount) of about 10 vol% to about 30 vol%, for example, about 15 vol% to about 20 vol%, based on the total volume of the solvent. When the content of fluoroethylene carbonate is within any of these ranges, cycle life characteristics can be improved.

The additive may include a first additive represented by chemical formula 1, and may further include at least one selected from a second additive represented by chemical formula 2, a third additive represented by chemical formula 3, and a fourth additive represented by chemical formula 4. In some embodiments, the additive includes a first additive represented by chemical formula 1, and further includes at least one selected from a second additive represented by chemical formula 2, a third additive represented by chemical formula 3, and a fourth additive represented by chemical formula 4.

Hereinafter, each of the first to fourth additives will be described.

First additive

The first additive may be a disilane compound represented by chemical formula 1. The first additive may be used singly or in a mixture of two or more (for example, only one compound represented by chemical formula 1 may be used, or a mixture of two or more different compounds each represented by chemical formula 1 may be used).

Chemical formula 1

In chemical formula 1, R¹To R³May each be independently selected from C1 to C8 alkyl groups substituted or unsubstituted with "vinyl or C1 to C5 alkyl" and not including a double bond, C1 to C8 alkyl groups substituted or unsubstituted with "vinyl or C1 to C5 alkyl" and including a double bond, C2 to C8 alkenyl groups, C5 to C8 cycloalkyl groups, C6 to C8 aryl groups, and fluorine atoms. For example, the C1 to C8 alkyl group may be an unsubstituted C1 to C8 alkyl group or a substituted C1 to C8 alkyl group having a vinyl group or a C1 to C5 alkyl group, wherein the C1 to C8 alkyl group does not include a double bond (except for the optional vinyl group). In some embodiments, the C1 to C8 alkyl group may be an unsubstituted C1 to C8 alkyl group or a substituted C1 to C8 alkyl group having a vinyl group or a C1 to C5 alkyl group, wherein the C1 to C8 alkyl group is a C2 to C8 alkyl group including a double bond (in addition to the optional vinyl group). The C1 to C8 alkyl group may be, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, sec-pentyl, tert-pentyl, hexyl, sec-hexyl, heptyl, sec-heptyl, octyl, sec-octyl, 2-methylpentyl, 2-ethylhexyl, etc. C2 to C8 alkenyl groups may be, for example, 1, 3-butadienyl, 1, 2-allenyl, 1, 4-pentadienyl, ethenyl, propenyl, isopropenyl, butenyl, pentenyl, hexenyl, 1-propen-2, 3-diyl, ethynyl, propynyl, butynyl, pentynyl, hexynyl, and the like. C5 to C8 cycloalkyl can be, for example, cyclopentylCyclohexyl, cyclohexylmethyl, and the like. The C6 to C8 aryl group may be, for example, phenyl, tolyl, xylyl, or the like. The above substituents may each be independently substituted with a halogen atom, a vinyl group, a C1 to C5 alkyl group, or the like. For example, the C1 to C8 alkyl groups may or may not include a double bond.

C1 to C8 alkyl groups including a double bond (e.g., propyl groups including a double bond) may be represented by formula a, wherein a represents a binding site to an adjacent atom.

Chemical formula A

In chemical formula 1, R⁴May be selected from C1 to C8 alkylene groups, C2 to C8 alkynylene groups, C4 to C8 alkylene groups having at least one selected from ether groups and thioether groups, a compound having a plurality of-CF groups₂-C1 to C8 alkylene groups of a linker and C4 to C10 alkylene groups with "ether and thioether groups (e.g. sulfide groups). The C1 to C8 alkylene groups may or may not include at least one-CF₂-a linker. For example, R⁴May be of four-CF as represented by formula B through formula E₂-C5 to C8 alkylene of a linker.

Chemical formula B

Chemical formula C

Chemical formula D

Chemical formula E

The C1 to C8 alkylene group may be, for example, methylene, ethylene, propylene, butylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, 2-methylbutylene, and the like. C2 to C8 alkynylene may be, for example, ethynylene, propynyl, butynyl, pentynyl, hexynyl, heptynyl, octynyl, nonynyl, acetylene-1, 2-diyl and the like. The C4 to C8 alkylene group having at least one selected from an ether group and a sulfide group may be, for example, a C4 to C8 alkylene group including at least one selected from an oxygen atom and a sulfur atom (e.g., a sulfide group). Non-limiting examples of the C4 to C8 alkylene group having at least one selected from an ether group and a sulfide group include a 4-oxaheptylene group, a 5-oxanonylene group and the like. The C4 to C10 alkylene group having an ether group and a sulfide group (e.g., sulfide group) may be a C4 to C10 alkylene group including an oxygen atom and a sulfur atom. An ether group can be represented by-O- (e.g., can include-O-), and a thioether group (e.g., a sulfide group) can be represented by-S- (e.g., can include-S-). The above substituents may each be independently substituted with a halogen atom.

Non-limiting examples of the first additive include 1, 3-bis (difluoromethylsilyl) propane, 1, 2-bis (difluoromethylsilyl) ethane, 1, 2-bis (difluoroethylsilyl) ethane, 1-difluoromethylsilyl-2-difluoroethylsilyl ethane, 1-difluoromethylsilyl-2-difluoropropylsilyl ethane, 1,3, 3-tetraethyldisiloxane, 1, 3-difluoro-1, 1,3, 3-tetrapropyldisiloxane, 1, 3-difluoro-1, 1,3, 3-tetrabutyldisiloxane, 1, 3-difluoro-1, 1,3, 3-tetrapentyldisiloxane, 1, 3-difluoro-1, 1,3, 3-tetrahexyldisiloxane, 1, 2-bis (fluorodimethylsilyl) ethane, 1, 2-bis (fluorodiethylsilyl) ethane, 1, 2-bis (fluorodipropylsilyl) ethane, 1, 2-bis (fluorodibutylsilyl) ethane, 1-fluorodimethylsilyl-2-fluoroethylsilylethane, 1, 3-bis (fluorodimethylsilyl) propane, 1, 3-bis (fluorodiethylsilyl) propane, 1, 3-bis (fluorodipropylsilyl) propane, 1, 3-bis (fluorodibutylsilyl) propane, 1, 3-divinyl-1, 1,3, 3-tetraethyldisiloxane, 1, 3-divinyl-1, 1,3, 3-tetrapropyldisiloxane, 1, 3-divinyl-1, 1,3, 3-tetrabutyldisiloxane, 1, 3-divinyl-1, 1,3, 3-tetrapentyldisiloxane, 1, 3-divinyl-1, 1,3, 3-tetrahexyldisiloxane, 1, 3-diacetylene-1, 1,3, 3-tetramethyldisiloxane, 1, 3-diacetylene-1, 1,3, 3-tetraethyldisiloxane, 1, 3-diacetylene-1, 1,3, 3-tetrapropyldisiloxane, 1, 3-divinyl-1, 1,3, 3-tetrapentyldisiloxane, and the like.

In some embodiments, the first additive may include at least one selected from the disilane compounds represented by chemical formulas 1-1 to 1-9, and in some embodiments, may include at least one selected from the disilane compounds represented by chemical formulas 1-1 to 1-4.

Chemical formula 1-1

Chemical formula 1-2

Chemical formulas 1 to 3

Chemical formulas 1 to 4

Chemical formulas 1 to 5

Chemical formulas 1 to 6

Chemical formulas 1 to 7

Chemical formulas 1 to 8

Chemical formulas 1 to 9

Second additive

The second additive may be a disilane compound represented by chemical formula 2. The second additive may be used singly or in a mixture of two or more (for example, only one compound represented by chemical formula 2 may be used, or a mixture of two or more different compounds each represented by chemical formula 2 may be used).

Chemical formula 2

In chemical formula 2, R⁵May be selected from C2 to C6 alkylene groups having no double bond, C2 to C6 alkylene groups having a double bond, and C6 to C12 arylene groups. The C2 to C6 alkylene group may be, for example, ethenyl, propenyl, butenyl, pentamethylene, hexamethylene and the like. The C2 to C6 alkylene groups may include a double bond. For example, a C3 alkylene group having one double bond may be represented by formula F.

Chemical formula F

The C6 to C12 arylene group may be, for example, 1, 2-phenylene, 1, 4-phenylene, (1,1 '-biphenyl) -4,4' -diyl, or the like. The foregoing substituents may each be independently substituted with a halogen atom.

In chemical formula 2, R⁶To R¹¹May each independently be selected from C1 to C6 alkyl and C2 to C6 alkenyl. The C1 to C6 alkyl group may be, for example, methyl, ethyl, propyl, isopropyl, butyl, pentyl, 2-propynyl, 3-fluoropropyl, 3-fluorobutyl, 4-fluorobutyl, etc. The C2 to C6 alkenyl group may be, for example, 1, 3-butadienyl, 1, 2-propadienyl, 1, 4-pentadienyl, ethenyl, propenyl, isopropenyl, butenyl, pentenyl, hexenyl, and the like. The foregoing substituents may each be independently substituted with a halogen atom.

Non-limiting examples of the second additive may include: bis (trimethylsilyl) acetylene dicarboxylate, bis (ethyldimethylsilyl) acetylene dicarboxylate, bis (dimethylpropylsilyl) acetylene dicarboxylate, bis (dimethylbutylsilyl) acetylene dicarboxylate, bis (dimethylvinylsilyl) acetylene dicarboxylate, fumaric acid bis (trimethylsilyl), maleic acid bis (trimethylsilyl), phthalic acid bis (trimethylsilyl), isophthalic acid bis (trimethylsilyl), terephthalic acid bis (trimethylsilyl), methylenesuccinic acid bis (trimethylsilyl), and the like.

The second additive may include, for example, a compound represented by chemical formula 2-1, a compound represented by chemical formula 2-2, or a mixture thereof.

Chemical formula 2-1

Chemical formula 2-2

Third additive

The third additive may be an unsaturated phosphate compound represented by chemical formula 3. The third additive may be used singly or in a mixture of two or more (for example, only one compound represented by chemical formula 3 may be used or a mixture of two or more different compounds each represented by chemical formula 3 may be used).

Chemical formula 3

In chemical formula 3, R¹²And R¹³May each be independently selected from hydrogen and C1 to C8 alkyl. The C1 to C8 alkyl group may be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, sec-pentyl, tert-pentyl, hexyl, sec-hexyl, heptyl, sec-heptyl, octyl, sec-octyl, 2-methylpentyl, 2-ethylhexyl, and the like. In some embodiments, R¹²And R¹³May be selected from hydrogen, methyl, ethyl and propyl, in some embodiments, may be selected from hydrogen and methyl, in some embodiments, R¹²And R¹³May both be hydrogen. When R is¹²And R¹³Selected from the above groups (e.g., R)¹²And R¹³Both hydrogen), adverse effects on the movement of lithium ions can be prevented or reduced, and good charging characteristics can be obtained.

In chemical formula 3, R¹⁴May be selected from C1 to C8 alkyl, C2 to C8 alkenyl, C2 to C8 alkynyl and C1 to C8 haloalkyl groups substituted or unsubstituted with vinyl groups. Examples of the C1 to C8 alkyl group and the C2 to C8 alkenyl group may be respectively combined with R in chemical formula 1 herein¹To R³The examples provided are the same. Non-limiting examples of C2 to C8 alkynyl groups may include ethynyl, 2-propynyl (also referred to herein as "propargyl"), 3-butynyl, 1-methyl-2-propynyl, 1-dimethyl-2-propynyl, and the like. Non-limiting examples of the C1 to C8 haloalkyl group may include chloromethyl, trifluoromethyl, 2-fluoroethyl, 2-chloroethyl, 2,2, 2-trifluoroethyl, 2,2, 2-trichloroethyl, 1,2, 2-tetrafluoroethyl, pentafluoroethyl, 3-fluoropropyl, 2-chloropropyl, 3-chloropropyl, 2-chloro-2-propyl, 3,3, 3-trifluoropropyl, 2,2,3, 3-tetrafluoropropyl, heptafluoropropyl, 2-chlorobutyl, 3-chlorobutyl, 4-chlorobutyl, 3-chloro-2-butyl, 1-chloro-2-butyl, 2-chloro-1, 1-dimethylethyl, 3-chloro-2-methylpropyl, 5-chloropentyl, 3-chloro-2-methylpropyl, 3-chloro-2, 2-dimethyl, 6-chlorohexyl and the like. In some embodiments, R¹⁴Can be selected from methyl, ethyl, propyl, isopropyl,Butyl, pentyl, 2-propynyl, 3-chloropropyl, 3-chlorobutyl and 4-chlorobutyl, and in some embodiments may be selected from methyl, ethyl, propyl and 2-propynyl, and in some embodiments may be selected from ethyl and 2-propynyl. When R is¹⁴When any group selected from the above groups is used, the internal resistance of the rechargeable lithium battery may be reduced.

R¹²And R¹³Non-limiting examples of the third additive, each of which is a hydrogen atom, may include methyl bis (2-propynyl) phosphate, ethyl bis (2-propynyl) phosphate, propyl bis (2-propynyl) phosphate, butyl bis (2-propynyl) phosphate, pentyl bis (2-propynyl) phosphate, allyl bis (2-propynyl) phosphate, tris (2-propynyl) phosphate, 2-chloroethyl bis (2-propynyl) phosphate, 2,2, 2-trifluoroethyl bis (2-propynyl) phosphate, 2,2, 2-trichloroethyl bis (2-propynyl) phosphate, and the like.

R¹²Is methyl and R¹³Non-limiting examples of the third additive that is a hydrogen atom may include methyl bis (1-methyl-2-propynyl) phosphate, ethyl bis (1-methyl-2-propynyl) phosphate, propyl bis (1-methyl-2-propyl) phosphate, butyl bis (1-methyl-2-propynyl) phosphate, pentyl bis (1-methyl-2-propynyl) phosphate, allyl bis (1-methyl-2-propynyl) phosphate, 2-propynyl bis (1-methyl-2-propynyl) phosphate, tris (1-methyl-2-propynyl) phosphate, 2-chloroethyl bis (1-methyl-2-propynyl) phosphate, and the like, 2,2, 2-trifluoroethyl bis (1-methyl-2-propynyl) phosphate, 2,2, 2-trichloroethyl bis (1-methyl-2-propynyl) phosphate and the like.

R¹²And R¹³Non-limiting examples of the third additive, each of which is methyl, may include methyl bis (1, 1-dimethyl-2-propynyl) phosphate, ethyl bis (1, 1-dimethyl-2-propynyl) phosphate, propyl bis (1, 1-dimethyl-2-propynyl) phosphate, butyl bis (1, 1-dimethyl-2-propynyl) phosphate, pentyl bis (1, 1-dimethyl-2-propynyl) phosphate, allyl bis (1, 1-dimethyl-2-propynyl) phosphate, 2-propynyl bis (1, 1-dimethyl-2-propynyl) phosphate, tris (1, 1-dimethyl-2-propynyl) phosphate, 2-chloroethyl bis (1, 1-dimethyl-2-propynyl) phosphate,2,2, 2-trifluoroethyl bis (1, 1-dimethyl-2-propynyl) phosphate, 2,2, 2-trichloroethyl bis (1, 1-dimethyl-2-propynyl) phosphate and the like.

In some embodiments, the third additive may be selected from methyl bis (2-propynyl) phosphate, ethyl bis (2-propynyl) phosphate, propyl bis (2-propynyl) phosphate, butyl bis (2-propynyl) phosphate, pentyl bis (2-propynyl) phosphate, tris (2-propynyl) phosphate, and 2-chloroethyl bis (2-propynyl) phosphate, in some embodiments from ethyl bis (2-propynyl) phosphate, propyl bis (2-propynyl) phosphate, butyl bis (2-propynyl) phosphate, and tris (2-propynyl) phosphate, in some embodiments from ethyl bis (2-propynyl) phosphate, and tris (2-propynyl) phosphate.

The third additive may include, for example, at least one of unsaturated phosphate ester compounds represented by chemical formulas 3-1 to 3-8. For example, the third additive may include an unsaturated phosphate compound represented by chemical formula 3-1, an unsaturated phosphate compound represented by chemical formula 3-2, or a mixture thereof.

Chemical formula 3-1

Chemical formula 3-2

Chemical formula 3-3

Chemical formula 3-4

Chemical formula 3-5

Chemical formula 3-6

Chemical formula 3-7

Chemical formula 3-8

Fourth additive

The fourth additive may be an unsaturated phosphate compound represented by chemical formula 4. The fourth additive may be used singly or in a mixture of two or more (for example, only one compound represented by chemical formula 4 may be used, or a mixture of two or more different compounds each represented by chemical formula 4 may be used).

Chemical formula 4

In chemical formula 4, R¹⁵And R¹⁶May be independently selected from hydrogen and C1 to C8 alkyl. Examples of the C1 to C8 alkyl groups may be combined with R in chemical formula 1 herein¹To R³The examples provided are the same. In some embodiments, R¹⁵And R¹⁶May be independently selected from hydrogen, methyl, ethyl and propyl, in some embodiments, may be selected from hydrogen and methyl, in some embodiments, R¹⁵And R¹⁶May all be hydrogen. When R is¹⁵And R¹⁶Selected from the above groups (e.g., R)¹⁵And R¹⁶Both hydrogen), adverse effects on the movement of lithium ions can be prevented or reduced, and good charging characteristics can be obtained.

In chemical formula 4, R¹⁷May be selected from C1 to C8 alkyl, C2 to C8 alkenyl, C2 to C8 alkynyl and C1 to C8 haloalkyl. Examples of the C1 to C8 alkyl group and the C2 to C8 alkenyl group may be respectively combined with R in chemical formula 1 herein¹To R³The examples provided are the same. Examples of C2 to C8 alkynyl and C1 to C8 haloalkyl groups can be respectively combined with R in chemical formula 3 herein¹⁴The examples provided are the same. In some embodiments, R¹⁷May be selected from methyl, ethyl, propyl, isopropyl, butyl, pentyl, 2-propynyl, 3-chloropropyl, 3-chlorobutyl and 4-chlorobutyl, in some embodiments may be selected from methyl, ethyl, propyl and 2-propynyl, and in some embodiments may be selected from methyl and ethyl. When R is¹⁷When selected from the above groups, the internal resistance of the rechargeable lithium battery can be reduced.

In chemical formula 4, n may be 1 or 2. When n is 1 or 2, the reaction of phosphoric acid ester from the acetylene glycol as a raw material can be easily carried out in a high yield. When n is 2, the relevant moiety of chemical formula 4 (e.g., chemical formula 4 consisting of

_nThe moiety represented) may be represented by formula G.

Chemical formula G

non-limiting examples of the fourth additive in which n is 1 may include but-2-yne-1, 4-diol tetramethyldiphosphate, but-2-yne-1, 4-diol tetraethyldiphosphate, but-2-yne-1, 4-diol tetrapropyldiphosphate, but-2-yne-1, 4-diol tetraisopropyldiphosphate, but-2-yne-1, 4-diol tetrabutyldiphosphate, but-2-yne-1, 4-diol tetrapentyldiphosphate, but-2-yne-1, 4-diol tetrakis (2-propynyl) diphosphate, but-2-yne-1, 4-diol tetrakis (3-chloropropyl) diphosphate, but-2-yne-1, 4-diol tetrakis (3-chlorobutyl) diphosphate, n is 1, 4-diol tetramethyldiphosphate, but-2-yne-1, 4-diol tetraethyldiphosphate, n is 1, 2-butyne-1, 4-diol tetrakis (4-chlorobutyl) diphosphate, and the like. In some embodiments, the fourth additive may be selected from the group consisting of butyne-1, 4-diol tetramethyl diphosphate, butyne-1, 4-diol tetraethyl diphosphate, butyne-1, 4-diol tetrapropyl diphosphate, 2-butene-1, 4-diol tetrakis (2-propynyl) diphosphate, and the like, for example, may be selected from the group consisting of butyne-1, 4-diol tetramethyl diphosphate, butyne-1, 4-diol tetrakis (2-propynyl) diphosphate, and the like.

non-limiting examples of the fourth additive in which n is 2 may include 2, 4-hexadiyne-1, 6-diol tetramethyldiphosphate, 2, 4-hexadiyne-1, 6-diol tetraethyldiphosphate, 2, 4-hexadiyne-1, 6-diol tetrapropyldiphosphate, 2, 4-hexadiyne-1, 6-diol tetraisopropyldiphosphate, 2, 4-hexadiyne-1, 6-diol tetrabutyl diphosphate, 2, 4-hexadiyne-1, 6-diol tetrapentyldiphosphate, 2, 4-hexadiyne-1, 6-diol tetrakis (2-propynyl) diphosphate, 2, 4-hexadiyne-1, 6-diol tetrakis (3-chloropropyl) diphosphate, 2, 4-hexadiyne-1, 6-diol tetrapropyldiphosphate, etc, 2, 4-hexadiyne-1, 6-diol tetrakis (3-chlorobutyl) diphosphate, 2, 4-hexadiyne-1, 6-diol tetrakis (4-chlorobutyl) diphosphate, and the like. In some embodiments, the fourth additive may be selected from 2, 4-hexadiyne-1, 6-diol tetramethyl diphosphate, 2, 4-hexadiyne-1, 6-diol tetraethyl diphosphate, 2, 4-hexadiyne-1, 6-diol tetrapropyl diphosphate, 2, 4-hexadiyne-1, 6-diol tetra (2-propynyl) diphosphate, and the like, for example, may be selected from 2, 4-hexadiyne-1, 6-diol tetramethyl diphosphate, 2, 4-hexadiyne-1, 6-diol tetra (2-propynyl) diphosphate, and the like.

In some embodiments, the fourth additive may include at least one of the unsaturated phosphate compounds represented by chemical formulas 4-1 to 4-4, for example, may include the unsaturated phosphate compound represented by chemical formula 4-1, the unsaturated phosphate compound represented by chemical formula 4-2, or a mixture thereof.

Chemical formula 4-1

Chemical formula 4-2

Chemical formula 4-3

Chemical formula 4-4

The electrolyte solution including the first additive and at least one selected from the second additive to the fourth additive may improve cycle-life characteristics and storage characteristics of the battery at high temperatures. For example, the electrolyte solution may include a first additive and a second additive, a first additive and a third additive, or a first additive and a fourth additive. For example, the electrolyte solution may include: a first additive, a second additive, and a third additive; a first additive, a second additive, and a fourth additive; or the first additive, the third additive, and the fourth additive. For example, the electrolyte solution may include a first additive, a second additive, a third additive, and a fourth additive.

The first to fourth additives according to embodiments of the present disclosure may be better decomposed in an electrolyte solution, for example, at a lower potential than a solvent, or absorbed on the surface of a positive electrode active material, as compared to Hydrofluoroether (HFE). The first to fourth additives or decomposition products thereof may cover the positive electrode active material and may suppress or reduce decomposition of the hydrofluoroether. For example, the first to fourth additives themselves (or decomposition products thereof) may cover the positive electrode active material, and thus, contact between the hydrofluoroether and the positive electrode active material is suppressed or reduced. Accordingly, the formation of a high-resistance passivation film (which may otherwise be derived from a solvent (e.g., formed from a solvent), specifically from decomposition products of a hydrofluoroether) on the positive electrode active material may be suppressed or reduced, and the deterioration of the cycle characteristics of the battery and/or the gas generation of the electrolyte solution may be suppressed or reduced.

The additional effects of the first to fourth additives are described in more detail below.

The silane group at the terminal of the first additive can be easily associated with LiPF₆The hydrofluoric acid released in the electrolyte or a part of the electrolyte solution interacts, and therefore, the first additive may decompose earlier than the second to fourth additives at the associated dissociation point on the positive electrode, and a passivation film may be formed. For example, unsaturated groups (e.g., alkynylene, etc.) between two silane groups in the first additive can contribute to the formation of a passivation film. Then, the second additive is decomposed, and the carbonyl group in its structure imparts ionic conductivity to the passivation film. The third additive and the fourth additive are chemically highly stable than the first additive and the second additive, and have voltage-resistant characteristics (e.g., relative voltage resistance). The third additive and the fourth additive may be adsorbed on the positive electrode active material via the phosphate group sites and may be received on the passivation film derived from the first additive, and thus, a dense and low-resistance passivation film is formed and contact between the positive electrode active material and the hydrofluoroether is suppressed or reduced.

The first additive may be included in an amount of about 0.01 wt% to about 1.5 wt% (e.g., about 0.1 wt% to about 1.4 wt%, about 0.2 wt% to about 1.4 wt%, or about 0.4 wt% to about 1.3 wt%), based on the total weight of the electrolyte solution. When the content of the first additive is within any of these ranges, the cycle-life characteristics and storage characteristics of the battery may be significantly improved.

The second additive may be included in an amount of about 0.05 wt% to about 1.00 wt% (e.g., about 0.07 wt% to about 1.00 wt%, about 0.07 wt% to about 0.6 wt%, or about 0.1 wt% to about 0.6 wt%), based on the total weight of the electrolyte solution. When the content of the second additive is within any of these ranges, the cycle-life characteristics and storage characteristics of the battery may be significantly improved.

The third additive may be included in an amount of about 0.04 wt% to about 1.00 wt% (e.g., about 0.05 wt% to about 1.00 wt%, about 0.07 wt% to about 0.6 wt%, or about 0.1 wt% to about 0.6 wt%), based on the total weight of the electrolyte solution. When the content of the third additive is within any of these ranges, the cycle-life characteristics and storage characteristics of the battery may be significantly improved.

The fourth additive may be included in an amount of about 0.01 wt% to about 1.0 wt% (e.g., about 0.05 wt% to about 1.0 wt%, about 0.07 wt% to about 1.0 wt%, about 0.1 wt% to about 0.7 wt%, about 0.1 wt% to about 0.6 wt%, or about 0.1 wt% to about 0.4 wt%), based on the total weight of the electrolyte solution. When the content of the fourth additive is within any of these ranges, the cycle-life characteristics and storage characteristics of the battery may be significantly improved.

The electrolyte solution may further include various additives in addition to the first to fourth additives of the embodiments of the present disclosure. The various additional additives may include additives acting on the negative electrode, additives acting on the positive electrode, ester additives, carbonate additives, sulfate additives, phosphate additives, borate additives, acid anhydride additives, electrolyte additives, and the like. In some embodiments, at least one or at least two of such additives may be added to the electrolyte solution.

As described above, the electrolyte solution according to the embodiment of the present disclosure including the first additive and at least one selected from the second additive to the fourth additive may significantly improve cycle-life characteristics and storage characteristics of a rechargeable lithium battery including a positive electrode including a lithium-containing transition metal oxide as a positive electrode active material and the electrolyte solution including a hydrofluoroether.

Hereinafter, a method of manufacturing a rechargeable lithium battery is described.

The positive electrode 20 is manufactured by, for example, the following method. First, a mixture of a positive electrode active material, a conductive material, and a binder is dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a slurry. Next, the slurry is applied on the current collector 21 and dried to form the positive electrode active material layer 22. The coating method is not particularly limited, and may include a blade coating method, a roll coating method, and the like. The coating process described below may be performed according to the same (or substantially the same) method. Next, the positive electrode active material layer 22 is pressed to have a density in a desired or appropriate range, thus forming the positive electrode 20.

Negative electrode 30 may be manufactured according to the same (substantially the same) method as that used in forming positive electrode 20. For example, first, a mixture of the negative electrode active material and the binder is dispersed in a solvent of N-methyl-2-pyrrolidone, water, or the like to form a slurry, the slurry is coated on the current collector 31, and then the slurry is dried to form the negative electrode active material layer 32. Next, the negative electrode active material layer 32 is pressed to have a density in a desired or suitable range, thus forming the negative electrode 30.

The separator can be manufactured as follows. First, a resin composed of the porous layer and a water-soluble organic solvent are mixed at a weight ratio of about 5 to 10/about 90 to 95 to prepare a coating solution. Here, the water-soluble organic solvent may be, for example, N-methyl-2-pyrrolidone, dimethylacetamide (DMAc), tripropylene glycol (TPG), or the like. Next, the coating solution is coated to a thickness of about 1 μm to about 5 μm on both sides or one side of the substrate. The substrate coated with the coating solution is then treated with a coagulation solution to coagulate the resin in the coating solution, thereby forming the separator. Here, the treatment of the substrate with the coagulation solution may include, for example, dipping the substrate in the coagulation solution, blowing the coagulation solution to the substrate, and the like. The coagulating solution can be obtained by mixing, for example, a water-soluble organic solvent with water. The amount of water may be in the range of about 40% to about 80% by volume based on the total volume of the coagulation solution. Next, the separator is washed with water and dried to remove water and the water-soluble organic solvent from the separator.

Then, a separator is interposed between the positive electrode 20 and the negative electrode 30, thus manufacturing an electrode structure. When the porous layer is formed on one side of the substrate, the negative electrode 30 is made to face the porous layer. Then, the electrode structure is manufactured to have a desired shape, such as the shape of a cylinder, a prism, a laminate, a button, etc., and then inserted into a container having the same shape. Then, in order to impregnate the electrolyte solution into the pores of the separator, the electrolyte solution according to the embodiment of the present disclosure is injected into a container, thus manufacturing a rechargeable lithium battery.

Hereinafter, embodiments of the present disclosure are explained in more detail with reference to examples. However, these examples are provided for illustrative purposes only and should not be construed as limiting the scope of the present disclosure. In addition, it should be apparent to those of ordinary skill in the art of lithium batteries that are not described in this disclosure, and therefore, will not be described here.

Example 1

98 wt% LiCoO₂1 wt% of polyvinylidene fluoride and 1 wt% of ketjen black were dispersed in N-methyl-2-pyrrolidone to prepare a slurry, and the slurry was coated on an aluminum current collector film as a current collector and dried, thereby forming a positive electrode active material layer. Next, the positive electrode active material layer was pressed to have a thickness of 4.0g/cm³Thus manufacturing a positive electrode.

90 wt% of a negative electrode active material obtained by mixing a silicon alloy (containing 70 atomic% of silicon) and artificial graphene in a weight ratio of 30:70, 7 wt% of polyacrylic acid, and 2 wt% of conductive carbon were dispersed in water to prepare a slurry, and the slurry was coated on an aluminum current collecting film as a current collector and dried, thereby forming a negative electrode active material layer. Subsequently, the negative electrode active material layer was pressed with a press machine to have a thickness of 1.45g/cm³Thus manufacturing a negative electrode.

A separator (20 μm thick, Mitsubishi Resin, Inc.) was then disposed between the positive and negative electrodes, thus fabricating an electrode structure.

Next, the electrode structure is inserted into the test vessel.

By mixing fluoroethylene carbonate (FEC) as Hydrofluoroether (HFE), Ethyl Methanesulfonate (EMS), dimethyl carbonate (DMC) and H (CF) in a volume ratio of 12:3:45:40₂)₂CH₂O(CF₂) H and LiPF₆Dissolved therein at a concentration of 1.3mol/L to prepare a base electrolyte solution. Next, the first additive represented by chemical formula 1-1 and the third additive represented by chemical formula 3-1 are added to the base electrolyte solution, thereby preparing an electrolyteAnd (3) solution. The first additive is used in an amount of 0.2 wt% based on the total weight of the electrolyte solution, and the third additive is used in an amount of 0.2 wt% based on the total weight of the electrolyte solution.

The obtained electrolyte solution was then placed in a test container and the opening thereof was sealed, thus manufacturing a rechargeable lithium battery cell according to example 1.

Examples 2 to 18 and comparative examples 1 to 10

Rechargeable lithium battery cells were independently manufactured according to the same (or substantially the same) method as that in example 1, except that the kinds and amounts of additives were changed as shown in tables 1 and 2 below.

(evaluation)

Evaluation 1: SEM photograph

Fig. 2 is a graph showing the charge distribution of LiCoO after the rechargeable lithium battery cells according to example 1 and comparative example 1 were stored at 60 ℃ for 24 hours₂Scanning Electron Microscope (SEM) photograph of the state of the passivation film on the surface of the particles.

Referring to fig. 2, regarding comparative example 1, when SEM images were taken, it was found that LiCoO was present₂Beam marks on the surface of the particles (part of the image surrounded by white squares). It is therefore considered that in the cell of comparative example 1, unlike in the cell of example 1, a passivation film derived from Hydrofluoroether (HFE) (for example, a decomposition product derived from HFE) was formed on LiCoO₂On the surface of the particles.

Evaluation 2: cycle life test

Cycle life tests were performed using the rechargeable lithium battery cells according to examples 1 to 18 and comparative examples 1 to 10.

Specifically, rechargeable lithium battery cells were each charged at 0.2mA/cm at 25 deg.C²The constant current/constant voltage is charged to a battery voltage of 4.4V and discharged to a battery voltage of 3.0V. This charge and discharge cycle was performed twice.

Next, rechargeable lithium battery cells were each charged at 45 ℃ at 2mA/cm²Constant current/constant voltage charging to a cell voltage of 4.4V and at 2mA/cm²Constant current discharge to 3.0VCell voltage, 300 such charge and discharge cycles were performed.

Then, the discharge capacity (mAh) per cycle was measured. The discharge capacity was measured by using TOSCAT-3000(Toyo System co., Ltd.).

The subsequent tables 3 and 4 show the capacity retention (relative to its initial discharge capacity considered as 100% capacity at 45 ℃) of the rechargeable lithium battery after 300 cycles as a result of the cycle test.

Evaluation 3: storage testing

The storage test was performed using the rechargeable lithium battery cells according to examples 1 to 18 and comparative examples 1 to 10.

Specifically, rechargeable lithium battery cells were each charged at 0.2mA/cm at 25 deg.C²The constant current/constant voltage is charged to a battery voltage of 4.4V and discharged to a battery voltage of 3.0V. Such charge and discharge cycles were performed twice, and the discharge capacity at the second cycle was regarded as an initial value of 100% capacity.

Next, rechargeable lithium battery cells were each charged at 0.2mA/cm at 25 deg.C²The cell was charged to a constant current/constant voltage of 4.4V, moved to a 60 ℃ chamber and allowed to stand for 30 days.

In addition, the rechargeable lithium battery cell was then moved to a room at 25 ℃, allowed to stand for 12 hours, and charged at 0.2mA/cm²To a cell voltage of 3.0V. Here, the discharge capacity under these conditions was regarded as the residual capacity, the ratio of the residual capacity to the capacity before storage in the room at 60 ℃ (i.e., the initial discharge capacity at the second cycle and 25 ℃ was regarded as 100% capacity) was calculated for each unit, and the results are shown in tables 3 and 4 below.

In addition, the increase ratio of the battery volume before measuring the remaining capacity to the battery volume before storing in the chamber at 60 ℃ (taken as 100% volume) was measured for each unit, and the results are shown in table 4.

TABLE 1

TABLE 2

TABLE 3

TABLE 4

In tables 1 and 2, "SN" means succinonitrile, "VC" means vinylene carbonate, "PS" means 1, 3-propane sultone, "LiFOB" means lithium difluorooxalato borate, and "LiBOB" means lithium dioxaoxalato borate. The amounts of these additives are shown in units of wt% based on the total weight of the electrolyte solution (base electrolyte solution (solvent) + additives). Further, "-" means that the corresponding additive is not used.

Referring to tables 3 and 4, most of the cells of examples 1 to 18 using the first additive and at least one selected from the second additive to the fourth additive showed increased capacity retention rate, low battery volume increase rate, and increased residual capacity after storage after 300 cycles, as compared to comparative examples 1 to 10. Accordingly, the cycle-life characteristics and storage characteristics of the battery may be improved by including the first additive and at least one selected from the second additive to the fourth additive according to the embodiments of the present disclosure to the base electrolyte solution.

In addition, when the amount of the first additive is in a narrower range of 0.1 wt% to 1 wt% (e.g., 0.2 wt% to 0.8 wt% or 0.4 wt% to 0.8 wt%), the cycle-life characteristics and storage characteristics of the corresponding battery are further improved.

Example 19

As shown in table 5 that follows, with respect to example 1, a rechargeable lithium battery cell was manufactured according to the same (or substantially the same) method as that of example 1, except that the composition of the base electrolyte solution and the kind and amount of the additive added to the base electrolyte solution were changed.

Examples 20 to 44 and comparative example 11

As shown in table 5 that follows, rechargeable lithium battery cells were manufactured according to the same (or substantially the same) method as that of example 19, except that the kinds and amounts of additives were changed.

(evaluation)

Evaluation 4: cycle life test

Cycle tests using the rechargeable lithium battery cells according to examples 19 to 44 and comparative example 11 were performed.

Next, rechargeable lithium battery cells were each charged at 45 ℃ at 2mA/cm²Constant current/constant voltage charging to a cell voltage of 4.4V and will be at 2mA/cm²The battery was discharged to a battery voltage of 3.0V at a constant current, and 200 such charge and discharge cycles were performed.

In table 6 below, the capacity retention rate after 200 cycles (relative to the initial discharge capacity at 45 ℃ that is considered as 100% capacity) is shown as the cycle test result.

Evaluation 5: storage testing

A storage test using the rechargeable lithium battery cells according to examples 19 to 44 and comparative example 11 was performed.

Specifically, rechargeable lithium battery cells were each charged at 0.2mA/cm at 25 deg.C²The constant current/constant voltage is charged to a battery voltage of 4.4V and discharged to a battery voltage of 3.0V. This charge and discharge cycle was performed twice, and the discharge capacity at the second cycle was considered to be 100% capacity.

Next, rechargeable lithium battery cells were each charged at 0.2mA/cm at 25 deg.C²The cell was charged to a battery voltage of 4.4V at constant current/constant voltage, and moved to a chamber at 60 ℃ and allowed to stand for 15 days.

In addition, the rechargeable lithium battery cell was then moved to a room at 25 ℃, allowed to stand for 12 hours, and charged at 0.2mA/cm²To a cell voltage of 3.0V.

Here, the discharge capacity measured under the above conditions was regarded as a residual capacity, the ratio of the residual capacity to the capacity before storage in a room at 60 ℃ (i.e., the initial discharge capacity at 25 ℃ for the second cycle was regarded as 100% capacity) was measured for each unit, and the results are shown in table 6 below.

In addition, the increase ratio of the battery volume before measuring the remaining capacity to the battery volume before being stored in a room at 60 ℃ (considered as 100% volume) was measured for each unit, and the results are shown in table 6 below.

TABLE 5

TABLE 6

In table 5, the amount of each component means wt% based on the total weight of the electrolyte solution (base electrolyte solution + additive), and in addition, "-" means that the corresponding additive is not added.

Referring to table 6, the first additive shows improved cycle life characteristics and storage characteristics in the following order from the maximum improvement to the minimum improvement: chemical formulas 1-4 (e.g., in example 22) > chemical formulas 1-3 (e.g., in example 21) > chemical formulas 1-1 (e.g., in example 19) > chemical formulas 1-2 (e.g., in example 20).

In addition, when the second additive is used within a narrow range of 0.07 wt% to 1 wt% (e.g., 0.07 wt% to 0.4 wt% or 0.1 wt% to 0.4 wt%), the cycle-life characteristics and storage characteristics of the battery are further improved.

In addition, when the third additive is used within a narrow range of 0.07 wt% to 1 wt% (e.g., 0.07 wt% to 0.6 wt% or 0.1 wt% to 0.6 wt%), the cycle-life characteristics and storage characteristics of the battery are further improved.

In addition, when the fourth additive is used in a narrow range of 0.1 to 0.6 wt% (e.g., 0.1 to 0.4 wt%), the cycle-life characteristics and storage characteristics of the battery are further improved.

While the disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents.

As used herein, expressions of "at least one of … …", "one of … …", "at least one of … …", and "one of … …" modify a column of elements by modifying the column elements, rather than modifying individual elements of the column. In addition, the use of "may" in describing embodiments of the invention refers to "one or more embodiments of the invention.

Additionally, as used herein, the terms "use," "utilizing," and variations thereof may be considered synonymous with the terms "utilize" and variations thereof, respectively.

As used herein, the terms "substantially," "about," and similar terms are used as approximate terms and not as degree terms, and are intended to account for inherent deviations in measured or calculated values that would be recognized by one of ordinary skill in the art.

Moreover, any numerical range recited herein is intended to include all sub-ranges subsumed within the recited range with the same numerical precision. For example, a range of "1.0 to 10.0" is intended to include all sub-ranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, i.e., having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0 (such as, for example, 2.4 to 7.6). Any maximum numerical limit recited herein is intended to include all lower numerical values subsumed therein, and any minimum numerical limit recited in this specification is intended to include all upper numerical values subsumed therein. Accordingly, applicants reserve the right to modify the specification (including the claims) to specifically enumerate any sub-ranges that fall within the ranges specifically enumerated herein.

Description of some reference numerals

10: rechargeable lithium battery

20: positive electrode

21: current collector

22: positive electrode active material layer

30: negative electrode

31: current collector

32: negative electrode active material layer

40: baffle plate layer

Claims

1. A rechargeable lithium battery, comprising:

a positive electrode including a positive active material; and

an electrolyte solution comprising a solvent and an additive,

wherein the positive electrode active material includes a lithium-containing transition metal oxide,

the solvent includes a hydrofluoroether and a water-soluble organic solvent,

the additive comprises:

a first additive represented by chemical formula 1, and

at least one additional additive selected from the group consisting of a second additive represented by chemical formula 2, a third additive represented by chemical formula 3, and a fourth additive represented by chemical formula 4:

chemical formula 1

Wherein, in chemical formula 1,

R¹to R³Are each independently selected from the group consisting of C1 to C8 alkyl groups substituted or unsubstituted with a vinyl group or C1 to C5 alkyl group and not including a double bond, C1 to C8 alkyl groups substituted or unsubstituted with a vinyl group or C1 to C5 alkyl group and including a double bond, C2 to C8 alkenyl groups, C5 to C8 cycloalkyl groups, C6 to C8 aryl groups, and fluorine atoms,

R⁴selected from C2 to C8 alkynylene, C4 to C8 alkylene having at least one selected from ether and thioether groups, having a plurality of-CF₂-a C1 to C8 alkylene group of a linker and a C4 to C10 alkylene group having an ether group and a thioether group,

chemical formula 2

Wherein, in chemical formula 2,

R⁵selected from the group consisting of C2 to C6 alkylene having no double bond, C2 to C6 alkylene having a double bond, and C6 to C12 arylene,

R⁶to R¹¹Are independently selected from C1 to C6 alkyl and C2 to C6 alkenyl,

chemical formula 3

Wherein, in chemical formula 3,

R¹²and R¹³Are each independently selected from hydrogen and C1 to C8 alkyl,

R¹⁴selected from the group consisting of C1 to C8 alkyl, C2 to C8 alkenyl, C2 to C8 alkynyl and C1 to C8 haloalkyl groups substituted or unsubstituted with a vinyl group,

chemical formula 4

Wherein, in chemical formula 4,

R¹⁵and R¹⁶Are each independently selected from hydrogen and C1 to C8 alkyl,

R¹⁷selected from C1 to C8 alkyl, C2 to C8 alkenyl, C2 to C8 alkynyl and C1 to C8 haloalkyl,

n is a number of 1 or 2,

wherein the hydrofluoroether is included in an amount of 35% to 50% by volume, based on the total volume of the solvent.

2. A rechargeable lithium battery as claimed in claim 1, wherein the hydrofluoroether comprises CF₃CH₂OCH₃、CF₃CH₂OCHF₂、CF₃CF₂CH₂OCH₃、CF₃CF₂CH₂OCHF₂、CF₃CF₂CH₂OCF₂CF₂H、HCF₂CF₂OCH₃、HCF₂CF₂OCH₂CH₃、HCF₂CF₂OC₃H₇、HCF₂CF₂OC₄H₉、H(CF₂)₂CH₂O(CF₂)H、HCF₂CF₂OCH₂CH(CH₃)₂、HCF₂CF₂OCH₂C(CH₃)₃、HCF₂CF₂OCH₂CF₃、HCF₂CF₂OCH₂CF₂CF₂H、(CF₃)₂CHOCH₃、(CF₃)₂CHCF₂OCH₃、CF₃CHFCF₂OCH₃、CF₃CHFCF₂OCH₂CH₃、CF₃CHFCF₂CH₂OCHF₂Or mixtures thereof.

3. A rechargeable lithium battery as claimed in claim 1, wherein the first additive is included in an amount of 0.01 wt% to 1.5 wt% based on the total weight of the electrolyte solution.

4. A rechargeable lithium battery according to claim 3, wherein the additive includes a first additive and a second additive,

the second additive is included in an amount of 0.05 wt% to 1.00 wt%, based on the total weight of the electrolyte solution.

5. A rechargeable lithium battery as claimed in claim 3, wherein said additive comprises a first additive and a third additive,

the third additive is included in an amount of 0.04 wt% to 1.00 wt%, based on the total weight of the electrolyte solution.

6. A rechargeable lithium battery according to claim 3, wherein the additive includes a first additive and a fourth additive,

the fourth additive is included in an amount of 0.01 wt% to 1.00 wt%, based on the total weight of the electrolyte solution.

7. The rechargeable lithium battery of claim 1, wherein the first additive includes at least one selected from the group consisting of compounds represented by chemical formulas 1-1 to 1-9:

chemical formula 1-1

Chemical formula 1-2

Chemical formulas 1 to 3

Chemical formulas 1 to 4

Chemical formulas 1 to 5

Chemical formulas 1 to 6

Chemical formulas 1 to 7

Chemical formulas 1 to 8

Chemical formulas 1 to 9

8. A rechargeable lithium battery as claimed in claim 1, wherein the second additive is selected from the group consisting of a compound represented by chemical formula 2-1, a compound represented by chemical formula 2-2, and a mixture thereof:

chemical formula 2-1

Chemical formula 2-2

9. A rechargeable lithium battery as claimed in claim 1, wherein the third additive includes at least one selected from the group consisting of compounds represented by chemical formulas 3-1 to 3-8,

chemical formula 3-1

Chemical formula 3-2

Chemical formula 3-3

Chemical formula 3-4

Chemical formula 3-5

Chemical formula 3-6

Chemical formula 3-7

Chemical formula 3-8

10. A rechargeable lithium battery as claimed in claim 1, wherein the fourth additive includes at least one selected from the group consisting of compounds represented by chemical formulas 4-1 to 4-4,

chemical formula 4-1

Chemical formula 4-2

Chemical formula 4-3

Chemical formula 4-4

11. A rechargeable lithium battery according to claim 1, wherein the lithium-containing transition metal oxide is a lithium cobalt-based composite oxide.

12. A rechargeable lithium battery as claimed in claim 1, further comprising a negative electrode including a negative active material,

wherein the anode active material includes at least one selected from a carbon-based material, a silicon-based material, a tin-based material, a lithium metal oxide, and metallic lithium.

13. A rechargeable lithium battery according to claim 1, wherein the solvent further comprises fluoroethylene carbonate.

14. A rechargeable lithium battery according to claim 13, wherein fluoroethylene carbonate is included in an amount of 10 to 30 vol%, based on the total volume of solvent.

15. A rechargeable lithium battery as claimed in claim 1, wherein the redox potential of the rechargeable lithium battery is relative to Li/Li⁺Greater than or equal to 4.3V and less than or equal to 5.0V.